1. Field of the Invention
The present invention relates to a lighting device.
2. Description of the Related Art
In general, a light emitting device package, including a light emitting device emitting light according to an application of an electrical signal thereto, has been widely used in various electronic products and mobile communications terminals, such as personal cellular phones, personal digital assistants (PDAs) and the like.
Recently, with an increase in light emitting device efficiency, the range of applications of a light emitting device package has been extended, and a secondary lens has been required for various applications of a light emitting device package.
Here, the secondary lens refers to a lens formed such that light emitted from a light emitting device has a radiation angle corresponding to the usual purpose and application field thereof.
The secondary lens may be mounted on a substrate so as to accommodate the light emitting device and a primary lens therein. Methods or structures for mounting the secondary lens on the substrate may be variously designed.
In general, methods of mounting a secondary lens on a substrate according to the related art may include a method of attaching a secondary lens directly to a substrate and a method of using a separate pillar allowing for the fixation of the secondary lens. These methods may be referred to as a direct attachment method and a pillar structure attachment method.
The method of attaching a secondary lens directly to a substrate (“direct attachment method”) may be more economically advantageous than a method of mounting a secondary lens on a substrate by using a separate device. However, the direct attachment method may be disadvantageous in that the function thereof capable of protecting the light emitting device package and the secondary lens from external circumstances is defective.
In addition, since the secondary lens needs to be attached directly to the substrate, an attachment area wider than a diameter of the lens may be required.
Moreover, the pillar structure attachment method is a method of fixing a secondary lens by using a separate pillar-shaped device, and may be disadvantageous, in that the arrangement and optical performance of lenses may have adverse effects due to the deformation of the pillar-shaped device (deformation in a pillar shape).
In addition, the pillar structure attachment method may require an attachment area wider than a diameter of the lens, similarly to the direct attachment method, and in the pillar structure attachment method, the precise arrangement of the light emitting device package may not be facilitated due to the injection molding of the pillar.
Thus, a technique of stably supporting a secondary lens while overcoming the above disadvantages is required.